This invention relates in general to apparatus for handling, testing and sorting electronic components. More specifically, it relates to an inverter system that reorients axial lead devices being processed by magnetic handling.
In the manufacture and use of electronic components, it is necessary to test each component reliably before it is shipped or assembled into a product. Production economics also place a high premium on the testing speed.
Certain types of electronic devices, at least for testing and handling purposes, are classified as "axial lead", that is, they have a body and two leads that extend from opposite ends of the body along generally the same axis. Resistors and diodes are common axial lead devices. The testing of diodes is complicated by the fact that they are electrically asymmetrical, that is, they present different electrical characteristics depending on which direction an electrical current flows through them. It is also significant that the leads of the devices are magnetic or paramagnetic. This allows them to be suspended horizontally in magnetic bins that have permanent magnets in their side walls, as described in Western Electric's U.S. Pat. No. 3,388,795 to Beroset et al and in the Beroset et al article "Using Magnetic Suspension to Float Small Parts" appearing at pp. 76-81 of Automation (May, 1968).
Testing and sorting apparatus for axial lead devices, including diodes, are known. Daymarc Corporation, the assignee of the present application, manufactures and sells a Model 1620 tester/sorter that directs the devices to a horizontal table that indexes to carry the device through a test station. Depending on the results of the tests, the devices are directed to one of several collecting bins. The processing speed of the Model 1620 tester/sorter is over 10,000 devices per hour, with a maximum rate of approximately 14,000 devices per hour.
A more recent tester/sorter, the Daymarc Model 1720, using a different handling and testing approach to achieve testing speeds in excess of 30,000 devices per hour. The devices are loaded into a conventional magnetic input bin that extends generally horizontally. It feeds a magnetic carrier wheel that picks up the devices and transports them, one by one, under a pair of "flying" test assemblies. After testing, the devices continue to rotate to one of several circumferential locations where they are stripped from the carrier wheel to either a main magnetic output bin or one of several vertically oriented collecting bins. The test result controls the strippers and therefore the location where the device is unloaded from the carrier wheel. Most of the devices, usually those that test out as being satisfactory and have the same preselected electrical orientation, are directed to the main output bin, which also extends generally horizontally and is generally aligned with the input bin. The movement or "flow" of devices through the tester/sorter is therefore generally horizontal.
One difficulty with the Model 1720 tester/sorter, and other horizontal flow test using magnetic handling apparatus known in the prior art, is that they do not have the capability to orient electrically asymmetrical devices reliably and quickly so that they all have the same electrical orientation. One solution is to pre-test the devices before they are loaded into the tester/sorter and then orient them uniformly. Western Electric's U.S. Pat. No. 3,731,783 to Dreher et al. describes a device that performs this task. It has two output bins, one for each of the two possible orientations of the devices. This solution has not proven to be practical, however, since it requires an additional steps--the pre-sort and then a combining of the devices from the two collecting bins. Another solution is to collect devices with different orientations in different bins. The difficulty here is that this requires two collecting bins for each sorting category. Because there are usually more than a few sorting categories, the result is that an unacceptably large total number of bins may be required.
Western Electric's U.S. Pat. No. 4,136,765 to Abraham et al. describes one attempt to improve on the Dreher et al. arrangement. Devices with one orientation are collected in an upper bin and then fed to a mechanical and magnetic spiral path that carries each device through a 180.degree. rotation as it descends to the lower collecting bin under the influence of gravity and air jets. The result is that all of the devices are collected in one bin, the lower bin, and they have the same electrical orientation. While this arrangement would appear to solve the "re-orientation problem," it has not proved to be commercially practical. One problem is that the spiral track is susceptible to jams, particularly where the leads are misaligned or bent.
While other types of testing apparatus, primarily ones using a vertical feed path, are known, the reorienting task is performed by arrangements that are tailored to the vertical mode of movement of the devices through the apparatus. U.S. Pat. No. 2,975,878 is exemplary of such a mechanical reorienting system and U.S. Pat. No. 3,702,438 is exemplary of a mechanical/magnetic system. In general, reorienting arrangements using gravity where the device is not under a continuous positive control have proven to have reliability problems. Heretofore, no reorienting apparatus has been able to operate as an integral component of a horizontal flow tester/sorter using magnetic handling, where the devices have a random orientation on input and a uniform orientation in a single output bin.
It is therefore a principal object of the present invention to provide an inverting system for a horizontal flow radial lead tester/sorter using magnetic handling where the inverter system operates rapidly and with a high degree of reliability.
Another principal object is to provide such an inverter system that operates in conjunction with a single main output bin so that all of the devices collected in the bin have the same electrical orientation.
A further object is to provide an inverter system with the foregoing advantages that is readily compatible with the Model 1720 tester/sorter manufactured and sold by Daymarc Corporation.
Another object is to provide an inverter system with the foregoing advantages that is not sensitive to misaligned or bent leads or to devices having varying masses or dimensions.
Yet another object is to provide an inverter system where the device being inverted is under a continuous positive control during the inversion.
A still further object is to provide an inverter system with all of the foregoing advantages that has a relatively uncomplicated construction and a favorable cost of manufacture.